[jboss-jira] [JBoss JIRA] (JGRP-2364) simply lock and unlock JGroups lock repeatedly will create chaos

[Bela Ban (Jira)]

     [ https://issues.jboss.org/browse/JGRP-2364?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bela Ban resolved JGRP-2364.
----------------------------
    Resolution: Done


Resolved. I changed one thing in your code though: you cannot set {{acquired}} and {{denied}} to false when there's no RELEASE_LOCK_OK: this would allow someone else to acquire the lock, and that should not be possible!
Scenario:
* A,B,C, C holds lock X
* A crashes, but  the new view \{B,C\} is not yet installed (e.g. because FD_ALL has a high timeout, and FD_SOCK is missing)
* C's unlock() request times out waiting for RELEASE_LOCK_OK
* If {{acquired}} and {{denied}} were set to false, a new locker would be able to acquire the lock
* This way, when view \{B,C\} is received by C, the RELEASE_LOCK request is resent to B and one reception of RELEASE_LOCK_OK, the lock is released, so someone else can acquire it.

> simply lock and unlock JGroups lock repeatedly will create chaos
> ----------------------------------------------------------------
>
>                 Key: JGRP-2364
>                 URL: https://issues.jboss.org/browse/JGRP-2364
>             Project: JGroups
>          Issue Type: Bug
>    Affects Versions: 4.1.1
>         Environment: JDK: 1.8
> JGroups: 4.1.1
> Lock: CENTRAL_LOCK
>            Reporter: Yong Deng
>            Assignee: Bela Ban
>            Priority: Major
>             Fix For: 4.1.2
>
>         Attachments: LockSimpleTest.java
>
>
> I have one simple use case to reproduce the issue. In same thread, just lock/unlock the lock repeatedly. Turn the log level to TRACE, you will find the communication chaos between the client and the coordinate. *JGroups unlock will return immediately after sending out RELEASE_LOCK currently. Why unlock don’t wait and only return after receiving the RELEASE_LOCK_OK response?*
> * Current log:
> {code:java}
> 16:56:40,399 TRACE [CENTRAL_LOCK] A --> A: GRANT_LOCK[sample-lock, lock_id=1, owner=A::31, trylock, timeout=10000]
> 16:56:40,404 TRACE [CENTRAL_LOCK] A <-- A: GRANT_LOCK[sample-lock, lock_id=1, owner=A::31, trylock, timeout=10000, sender=A]
> 16:56:40,410 TRACE [CENTRAL_LOCK] A --> A: LOCK_GRANTED[sample-lock, lock_id=1, owner=A::31]
> 16:56:40,411 TRACE [CENTRAL_LOCK] A <-- A: LOCK_GRANTED[sample-lock, lock_id=1, owner=A::31, sender=A]
> 16:56:40,413 TRACE [CENTRAL_LOCK] A --> A: RELEASE_LOCK[sample-lock, lock_id=1, owner=A::31]
> 16:56:40,414 TRACE [CENTRAL_LOCK] A <-- A: RELEASE_LOCK[sample-lock, lock_id=1, owner=A::31, sender=A]
> 16:56:40,414 TRACE [CENTRAL_LOCK] A --> A: RELEASE_LOCK[sample-lock, lock_id=1, owner=A::31]
> 16:56:40,415 TRACE [CENTRAL_LOCK] A --> A: RELEASE_LOCK_OK[sample-lock, lock_id=1, owner=A::31]
> 16:56:40,415 TRACE [CENTRAL_LOCK] A --> A: RELEASE_LOCK[sample-lock, lock_id=1, owner=A::31]
> {code}
> * The expected log:
> {code:java}
> 2019-07-24 17:01:52,849 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] --> [A] GRANT_LOCK [sample-lock, lock_id=1, owner=A::63, trylock (timeout=10000)
> 2019-07-24 17:01:52,849 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] <-- [A] GRANT_LOCK [sample-lock, lock_id=1, owner=A::63, trylock (timeout=10000)
> 2019-07-24 17:01:52,852 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] --> [A] LOCK_GRANTED [sample-lock, lock_id=1, owner=A::63 ]
> 2019-07-24 17:01:52,852 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] <-- [A] LOCK_GRANTED [sample-lock, lock_id=1, owner=A::63 ]
> 2019-07-24 17:01:52,853 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] --> [A] RELEASE_LOCK [sample-lock, lock_id=1, owner=A::63 ]
> 2019-07-24 17:01:52,853 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] <-- [A] RELEASE_LOCK [sample-lock, lock_id=1, owner=A::63 ]
> 2019-07-24 17:01:52,853 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] --> [A] RELEASE_LOCK_OK [sample-lock, lock_id=1, owner=A::63 ]
> 2019-07-24 17:01:52,854 TRACE [org.jgroups.protocols.CENTRAL_LOCK] [A] <-- [A] RELEASE_LOCK_OK [sample-lock, lock_id=1, owner=A::63 ]
> {code}



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